Collapsed cone dose calculations for heterogeneous tissues in brachytherapy using primary and scatter separation...

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Brachytherapy utilizes sealed sources for localized cancer treatment (gynecological, prostate, head/neck).
• Accurate dose calculation is critical for effective brachytherapy planning.
• Current TG-43 formalism inadequately models patient-specific tissue distribution and attenuation effects.

Purpose of the Study:

• To derive and implement a model-based dose calculation algorithm for brachytherapy.
• To improve upon the limitations of the TG-43 formalism in clinical treatment planning.

Main Methods:

• Developed a brachytherapy-specific collapsed-cone algorithm incorporating analytical ray tracing for primary photons.
• Included successive scattering dose calculations for photons.
• Detailed implementation within a commercial treatment planning system, addressing grid setup and applicator materials.

Main Results:

• Demonstrated the algorithm's application in gynecological and breast brachytherapy cases.
• Showcased the improved dose calculation accuracy compared to the TG-43 formalism in these clinical scenarios.

Conclusions:

• Model-based algorithms that account for 3D treatment geometry enhance dosimetric accuracy in brachytherapy.
• The provided derivations offer a robust foundation for clinical, educational, and research use in brachytherapy.